Question 989 of 1,663
DBS-C01 Workload-Specific Database Design Practice Question
An e-commerce application uses Amazon DynamoDB as its primary database. The table stores order data with a partition key of 'OrderID' and a sort key of 'OrderDate'. The application frequently queries orders by customer ID (which is not a key attribute). What design change would improve query performance?
⚠ Common exam trap
A common mix-up: candidates confuse Local Secondary Indexes (LSIs) with Global Secondary Indexes (GSIs), assuming an LSI can be used to query by a non-key attribute without the partition key, but LSIs require the same partition key as the base table and cannot be added after table creation.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a Global Secondary Index on CustomerID
Creating a Global Secondary Index (GSI) on CustomerID allows efficient querying by that attribute without scanning the entire table. A GSI has its own partition and sort keys, enabling fast lookups on non-key attributes. This directly addresses the performance issue of frequent queries by CustomerID, which otherwise would require a full table scan.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable DynamoDB Streams and export to Amazon Elasticsearch Service
Why it's wrong here
This adds complexity and latency; not optimal for simple query improvement.
- ✗
Use DynamoDB Accelerator (DAX) to cache queries
Why it's wrong here
DAX caches results but does not help with querying by non-key attributes.
- ✓
Create a Global Secondary Index on CustomerID
Why this is correct
GSI allows querying by CustomerID efficiently.
- ✗
Create a Local Secondary Index on CustomerID
Why it's wrong here
LSI requires same partition key; OrderID is the partition key, so LSI on CustomerID is not possible without changing table structure.
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Last reviewed: Jun 24, 2026
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